1. Field of the Invention
Embodiments of the present invention generally relate to a write head for use in a magnetic disk drive.
2. Description of the Related Art
The heart of a computer's long term memory is an assembly that is referred to as a magnetic disk drive. The magnetic disk drive includes a rotating magnetic disk, write and read heads that are suspended by a suspension arm adjacent to a surface of the rotating magnetic disk, and an actuator that swings the suspension arm to place the read and write heads over selected circular tracks on the rotating disk. The read and write heads are directly located on a slider that has an air bearing surface (ABS). The suspension arm biases the slider toward the surface of the disk, and when the disk rotates, air adjacent to the disk moves along with the surface of the disk. The slider flies over the surface of the disk on a cushion of this moving air. When the slider rides on the air bearing, the write and read heads are employed for writing magnetic transitions to and reading magnetic transitions from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
In order to meet the ever increasing demand for improved data rate and data capacity, researchers have recently been focusing their efforts on the development of perpendicular recording systems. A traditional longitudinal recording system stores data as magnetic bits oriented longitudinally along a track in the plane of the surface of the magnetic disk. This longitudinal data bit is recorded by a fringing field that forms between the pair of magnetic poles separated by a write gap.
A perpendicular recording system, by contrast, records data as magnetizations oriented perpendicular to the plane of the magnetic disk. The magnetic disk has a magnetically soft underlayer covered by a thin magnetically hard top layer. The perpendicular write head has a write pole with a very small cross section and a return pole having a much larger cross section. A strong, highly concentrated magnetic field emits from the write pole in a direction perpendicular to the magnetic disk surface, magnetizing the magnetically hard top layer. The resulting magnetic flux then travels through the soft underlayer, returning to the return pole where it is sufficiently spread out and weak that it will not erase the signal recorded by the write pole when it passes back through the magnetically hard top layer on its way back to the return pole.
In a perpendicular magnetic recording system, it is desirable to maximize write field strength and also maximize field gradient. A strong write field ensures that a magnetic bit can be recorded in the magnetically hard top layer of the magnetic medium. A high field gradient allows for sharper magnetic transitions, thereby reducing noise and increasing signal to noise ratio.
The market and competition continuously are pushing for higher recording area density, and higher area density necessitates the continuous improvement from write and read head performance. Wrap-around shield (WAS) heads have been used in HDD to meet the performance requirement of write heads (SNR and error rate). In the WAS head, the main pole is surrounded by shields from three sides from the ABS view. Another known solution to improve performance of perpendicular magnetic recording (PMR) heads is using a slanted pole on the trailing side of the writer. However, both of the solutions (the conventional WAS and the slanted write pole) start to show limitations in the current and future products.
Therefore, it is desirable to provide a perpendicular write head that has improved performance.